1. Field of the Invention
The present invention relates to a wireless transmission system. In particular, the present invention relates to a wireless transmission system, a wireless transmission device, and a wireless transmission terminal with which, when a wireless transmission terminal which is being used by a user and which is connected to a wireless transmission device accesses the internet, the wireless transmission device utilizes the public wireless transmission network.
In particular, the present invention relates to a wireless transmission system and to a moving wireless transmission device with which, when a wireless transmission terminal which is being used by a user and which is connected to a moving wireless transmission device accesses the internet, said moving wireless transmission device utilizes the public wireless transmission network.
In particular, the present invention relates to an authentication method for specifying a device which is the object of communication, and to a wireless transmission device and a wireless terminal device which take advantage of this authentication method.
In particular, the present invention relates to a traffic management system which performs vehicle traffic management by providing information to passengers (hereinafter termed “getting off information”) which is related to guiding them for getting off or the like, using a wireless transmission function which has been built into a public transport vehicle such as a bus or a train or the like.
2. Description of Related Art
In recent years, various types of wireless transmission system such as mobile telephones and wireless LANs (Local Area Networks) and the like have come into widespread use, and their accessibility has greatly increased.
For example, a household LAN can be easily set up as a wireless LAN, and it is easy to download electronic mail outside the home by using a mobile telephone, and it has become everyday practice to read home pages upon the internet in this manner.
Furthermore, wireless LAN services within vehicles such as buses or trains in which passengers ride for comparatively long time periods have been considered. With a wireless transmission system for implementing this type of wireless LAN service, a wireless LAN is set up by providing a wireless transmission device for the wireless LAN as a wireless base station within the moving vehicle. Furthermore, as an access method to external networks such as the internet or the like, this wireless transmission device is endowed with a function of connection to a mobile telephone network, which is a public wireless transmission network. By doing this, it is possible to connect to the internet from a terminal such as a wireless LAN terminal or the like which is being employed by the user within the moving vehicle, such as a notebook type personal computer or the like, via the wireless transmission device and the public wireless transmission network.
As this public wireless transmission network, a cellular system or a PHS system or the like may be considered, but in particular, there is a per se known high speed wireless transmission system according to the cdma2000 1xEV-DO standard; for example, refer to Japanese Patent Laying Open Publication 2002-300644.
However there are the following problems with, for example, a wireless LAN which is a wireless transmission system according to the above described prior art. Connection between a wireless transmission device and the public wireless transmission network is performed, according to requirements, when accessing from the wireless LAN terminal to a device upon the exterior, such as a web server upon the internet or the like. Due to this, when for example the wireless LAN terminal makes a request to example a home page, the wireless transmission device first starts a connection to the public wireless transmission network, and, when this connection has been completed, it starts to access the home page which is the objective. However, when connecting from a moving vehicle to the public wireless transmission network, sometimes a long time period is required for establishing this connection, due to reasons such as variability of the wireless propagation environment and the like. In particular, this can become prominent with a public wireless transmission network upon which the PPP (Point to Point Protocol) is used, for example a PHS (Personal Handyphone System), or a network of the so called “cdma2000 1xEV-DO” type (CDMA: Code Division Multiple Access).
Because of this, sometimes it happens that a timeout occurs when accessing a home page with an application (a browser) from the side of the wireless LAN terminal before the connection to the public wireless transmission network has been completed, and in practice, irrespective of whether or not access to the home page is actually possible, a message may be displayed upon the wireless LAN terminal to the effect that access to the home page which is the objective cannot be provided. From the point of view of the user, this means that he cannot know whether connection to the public wireless transmission network is impossible or will take a long time, or whether really it is not possible to access the home page which is the objective, and accordingly a feeling of uncertainty and disquiet is imparted to the user, so that these operational conditions are very bad. Furthermore, on the side of the wireless LAN terminal, there is the problem that the wireless transmission device undesirably accesses the wireless transmission network without any dependence upon whether or not a display is being provided to the effect that a timer of the application has timed out so that access to the home page cannot be established, which is useless.
Furthermore, with a wireless transmission system of the above described prior art type, such as for example a wireless LAN, the problems described below also occur.
When a wireless transmission device within a moving vehicle connects to a public wireless transmission network, it is not possible absolutely to guarantee success in establishing a connection, because of the fact that the state of wireless communication with the public wireless transmission network changes from moment to moment due to changes in the position of the vehicle. Furthermore, with a public wireless transmission network which uses the PPP (Point to Point Protocol), such as for example a PHS (Personal Handyphone System) or a CDMA (Code Division Multiple Access) system of the so called cdma2000 1xEV-DO type, the time which is required for connection changes according to the state of wireless communication and the number of users of the wireless communication system and so on. However, the state of wireless communication with the public wireless transmission network and the number of users of the public wireless transmission network are not known to the users within the moving vehicle. Due to this, although a user may be trying indefatigably to establish an internet connection via the public wireless transmission network, if the wireless transmission device is, for example, out of range of the service of the public wireless transmission network, then the wireless transmission terminal of the user is not able to connect to the internet. Furthermore, even if the wireless transmission terminal of the user is able to establish access to the internet, if the traffic upon the public wireless transmission network is congested, then the wireless transmission device of the user experiences an extremely slow response.
In other words, since from the point of view of the user he does not know the state of wireless communication between the wireless transmission device and the public wireless transmission network or the number of users of the public wireless transmission network, there is the problem that sometimes he does not know the reason why he cannot connect to the internet or the reason why the response is poor, even though he has established access to the internet.
Furthermore, the provision of a wireless LAN service within a moving vehicle such as a bus or a train in which passengers ride for a comparatively long time period is being considered. With a wireless transmission system for implementing such a wireless LAN service, the wireless LAN is set up by providing a mobile wireless transmission device for a wireless LAN as a wireless base station within the moving vehicle. Furthermore, as a method for accessing an exterior network such as the internet or the like, such a mobile wireless transmission device is endowed with a function for connection to a mobile telephone network, which is a public wireless transmission network. By doing this, it is possible to connect to the internet via the mobile wireless transmission device and the public wireless transmission network from a terminal for a wireless LAN or the like, such as a notebook type personal computer or the like, which is being used by a user within the moving vehicle.
Although, as such a public wireless transmission network, a cellular system or a PHS system or the like may be considered, in particular, as a high speed wireless transmission system, there is a known type of such system which utilizes the cdma2000 1xEV-DO format. For example, reference may be made to Japanese Patent Laying Open Publication 2002-300644.
However, there are the following problems with the above described prior art type wireless transmission systems.
When establishing a connection to the internet from a mobile wireless transmission device within the moving vehicle upon a request from the wireless LAN terminal, although a mobile telephone network—which is a public wireless transmission network—may be utilized, the communication speed of such a mobile telephone network is insufficient by comparison to that of a wireless LAN or the like, and accordingly it is difficult to provide a comfortable internet access environment. Furthermore, the state of wireless communication with the mobile telephone network may be bad due to the position of the vehicle or the like, and, if a large number of mobile telephone users who are utilizing the same base station outside the moving vehicle are present, then the communication speed becomes even slower.
In recent years, as a next generation high speed wireless transmission format, the cdma2000 1x-EV-DO format (hereinafter termed the EV-DO format) has been developed. This EV-DO format is a format according to the cdma2000 1x format which corresponds to an extended third generation cdmaOne format, and is a format which offers a specially increased speed transmission rate for data communications. Here, “EV” means “evolved”, and “DO” means “data only”.
With the EV-DO format, the wireless interface structure of the uplink circuit from the wireless transmission terminal to the base station is almost the same as that for the cdma2000 1X format. With regard to the wireless interface structure of the downlink circuit from the base station wire to the less transmission terminal, on the one hand, that for the band which is regulated at 1.23 MHz is identical to that for the cdma2000 1x format, while that for the modulation method or the multiplexed method is greatly different from that for the cdma2000 1x format. With the modulation method, by contrast to QPSK or HPSK which are used in the cdma2000 1x format, with the EV-DO format, QPSK, 8-PSK, or 16QAM are changed over between according to the reception conditions in the downlink circuit in the wireless transmission terminal. As a result, if the reception conditions are good, the error tolerance is low and moreover a high speed transmission rate is used, while, if the reception conditions are bad, although the speed is low, a transmission rate is used for which the error tolerance is high.
Furthermore, in a multiplexed method for performing communication simultaneously from a single base station to a plurality of wireless transmission terminals, CDMA (Code Division Multiple Access) which is used in the cdmaOne format or in the cdma2000 1x format is not utilized, but instead a TDMA (Time Division Multiple Access) method is employed, in which communication is performed with a plurality of wireless transmission terminals by dividing time into units of 1/600 sec, and by performing communication with a single wireless transmission terminal in each of these time units, and moreover by changing over the wireless transmission terminal which is the object of communication between each time unit and the next.
A wireless transmission terminal measures the carrier to interference power ratio of a pilot signal, as a quantity representative of the reception state of the downlink circuit from the base station which is the object of communication, and estimates the state of reception of the next reception timing from changes thereof, and notifies “the highest transmission speed at which it is possible to receive with less than a predetermined error rate” which is anticipated therefrom to the base station as a data rate control bit (hereinafter “DRC”). Here, this predetermined error rate is normally about 1%, although it depends upon the system design. The base station receives DRCs from a plurality of wireless transmission terminals, and a scheduler function within the base station determines, each time division unit, with which of the wireless transmission terminals to communicate; but, in concrete terms, as high a possible transmission rate is used in communication with each of the wireless transmission terminals, based upon the DRCs from the wireless transmission terminals.
With EV-DO, and with a downlink circuit which is made in the above described manner, it is possible to obtain a maximum transmission rate of 2.4 Mbps for each sector. However, this transmission rate is the sum, upon a single frequency band, and normally for one among a plurality of sectors thereof, of the data communication rates for the plurality of wireless transmission terminals which are connected to the single base station, and if a plurality of frequency bands are utilized, the transmission rate is also increased. For example, reference should be made to the previously mentioned Japanese Patent Laying Open Publication 2002-300644.
Apart from this type of EV-DO format, due to the extension of the regions in which LAN networks can be used to company or home environments, wireless LANs are also being developed, and recently wireless LANs which follow the IEEE802.11b standard are endowed with a capability of providing a maximum communication speed of 11 Mbps over a communication area of a radius of 50 to 100 m. Generally this diffusion is taking place due to the increase in transmission speed, the reduction in the cost of access points and mobile terminals, and the spreading of ADSL within the home environment. Furthermore, wireless networks are also being utilized outdoors, and support and service in a street environment is starting within rather limited areas. In other words, with a wireless LAN, by comparison to the EV-DO format, the service area is rather narrow, but it is possible to provide a higher transmission speed.
On the other hand, attention is also being given to provision of a wireless LAN within a vehicle such as a bus or a train or the like in which people ride for comparatively long time periods, and, within moving vehicles, communication devices are being provided which include communication means with a wireless LAN and communication means with mobile telephones, and notebook type PCs and the like within the vehicle are connected via this wireless LAN; and moreover, by connecting to the internet outside the vehicle by taking advantage of the mobile telephone network, it becomes possible for connection to be established from notebook type PCs or the like within the vehicle to the internet outside the vehicle. If such a wireless LAN within the vehicle is utilized, from the viewpoint of the service provider, it is necessary to implement an authentication procedure in order to prevent a person who is not authorized from establishing a wireless connection to the wireless LAN, and furthermore it is necessary to implement encryption in order to prevent leakage to an unintended user of the information which a user is transmitting. Normally, with a wireless LAN, as a method for making it impossible for an unauthorized user to connect to an access point, encryption keys (WEP) and MAC address registers and the like are employed. With a wireless LAN service within a vehicle or the like, limitation of the users by the use of MAC address registers cannot be performed, since wireless LAN cards or the like are not distributed to the persons who are to utilize the service. Because of this, a method is employed in which encryption keys which correspond to the access point are provided to the users in advance, and these encryption keys are set up in the terminals which are being employed by the users. Furthermore, if a charge is being made for the service itself, it is also possible to display a predetermined portal website when the user has wirelessly connected to the wireless repeater device, and to perform user authentication via a user name and a password.
Encryption for such a wireless LAN as described above can only normally be performed with a single encryption key for a single access point. Due to this, each of the users who is connected to a single access point utilizes the same encryption key. The security threshold between the users who are utilizing the same access point is low, and there is a danger that information which is being transferred via wireless transmission can be read out. In order to enhance the level of safety, it is necessary for each of the users to be provided with different encoding information and with different authentication information. When a normal type of WEP key is employed, and when this is made to correspond with an authentication procedure, at least when first connecting to the system, typically, while looking at a paper form which is distributed in advance upon which encoding information and authentication information are written, the user may input encoding information and authentication information such as a user name and a password or the like for the authentication procedure by using an input means such as a keyboard or the like while looking at his terminal screen. Normally, in the case of a moving vehicle such as a bus or a train or the like, people are sitting next to one another at such distances apart that their shoulders are in mutual contact. In this type of environment, the contents of such a paper form upon which the encoding information and the authentication information are written in advance can easily be seen by a person who is sitting next to the user, so that the level of security is not very reliable, and moreover the above mode of operation is quite troublesome for the user, since he is required to input the encryption key accurately while sitting in the bus or the train which may be swaying about, and such an encryption key is difficult for him to hold in his short term memory.
In recent years, there has been an tendency for the bandwidth of mobile telephone apparatus to be extended, and a maximum communication speed in the downlink direction of 2.4 Mbps has been implemented (for example, refer to the previously mentioned Japanese Patent Laying Open Publication 2002-300644). Furthermore, with a LAN which is used for networking an office or a household, generally nowadays a wireless LAN is set up, because it is very easy to implement and use. In this connection, in recent years, next generation wireless LANs which conform to the IEEE802.11b standard have generally become widely diffused, due to the increase in transmission speeds and the reduction in the costs of access points and of mobile terminals, and also because ADSL has also become very prevalent in the home environment. Furthermore, support service in the street (hereinafter termed street support service) and the like has also commenced, in which it becomes possible to utilize this type of wireless LAN outdoors by using a mobile telephone apparatus.
Furthermore, with a wireless LAN, the connections between terminals by physical cabling in a prior art type LAN are replaced by wireless links, so that there is a high affinity with a prior art type LAN which uses physical cabling. With this type of background, a wireless LAN of the current type is one which follows the IEEE302.11b standard, and at the maximum its transmission speed can be raised to 11 Mbps. It should be understood that, with this type of wireless LAN, the area of a single access point is narrowed down to a radius of about 50˜100 m, so that a street support service for mobile telephone equipment using this type of wireless LAN is a limited one in a limited area.
On the other hand, in recent years, the transmission speed of mobile telephone apparatus has become higher and higher along with the widening of its band, but as yet the transmission speed is still slow in comparison with a wireless LAN. However, the radius of the service area of a single access point has increased to about 2 km.
Furthermore, with a wireless LAN, a mobile IP technology has become widespread in which a large number of access points are set up, in the same way as with mobile telephone apparatus, and it is possible for a mobile node to access these access points continuously while traveling past them, without changing its IP address. With this type of mobile IP, there is a home agent, which is a router which has an interface upon a home link of a mobile node, and there is a foreign agent, which is a router which has an interface upon a mobile terminal link of a mobile node; and, furthermore, a mobile node acquires a care-of address upon the mobile terminal link, and registers this care-of address in the home agent as the care-of address of the mobile terminal. On the other hand, with a home agent, by transferring the packets which have been transmitted towards a mobile agent to the care-of address which has been encapsulated, there is no change in the IP address of the mobile node, and it becomes possible to transfer packets to the mobile node which is present upon the link to the mobile terminal.
Furthermore, with an ITS (Intelligent Transport System: a high quality road traffic system) which is an integration of a car navigation system and a wide area traffic management system, it is possible to anticipate an increase in the wireless transmission capabilities of the car navigation system, and, by connection through a mobile telephone apparatus or the like, it becomes possible to access the internet or the like, and to transmit and receive electronic mail and so on. Furthermore since, along with the reduction in cost of hard disks, it is also possible to access a CD (Compact Disk) or a DVD (Digital Versatile Disk) or the like at comparatively high speed, the accumulation of road information for car navigation systems upon DVDs or HDDs (Hard Disk Drives) has much progressed recently. Moreover, the implementation of systems which take advantage of wireless as an updating method for such road information is proceeding apace.
However, even if the user can verify a timetable which has been determined in advance for a moving vehicle such as a bus or a train, he cannot know traffic information such as through what locality the vehicle is passing at the moment in real time. Furthermore, if a delay due to traffic conditions or the like has occurred, the user cannot be aware in real time how the departure time instant from a stopping point such as his desired station, or the arrival time instant at such a stopping point, is being affected.